here is a map of the world, drawn 50 years before columbus; at its edge, the towers of paradise. and an immediate best seller, columbus' description of his voyage to the new world, published in 1493. in a certain way, the library is kind of the attic of western civilization. >> father michael collins: it's so true. and it's like many attics, you know? you put things up all the time. you keep on pushing over boxes to make space for more things. >> safer: father michael collins is an irish priest who's written extensively about the vatican, where the library's shelves, if you put them end to end, would stretch for 31 miles. is there anyone, any single person who really knows what the library holds? >> collins: nobody knows exactly what's there, because it will be impossible for the human brain to understand, to remember the titles, who wrote it, when they were written. >> monsignor cesare pasini: it is quite a treasure of humanity that you have here. >> safer: monsignor cesare pasini presides over the library. its great hall-- essentially unchanged over the centuries-- is a picture